For example, a copying machine having a double-sided copying function is provided with a paper-reversing device for reversing paper in its leading and rear portions in the paper-transporting direction. As shown in FIG. 48, for example, a conventional paper-reversing device of this type is provided with a tilted tray 202 for switching back. A sheet of paper, which is to be reversed, is dropped from an entrance-side paper guide 201 onto the tray 202, and the sheet of paper on the tray 202 is pushed out by a paper-stopping member 203, sucked by a transport belt 204, and sent out with its leading and rear portions in a reversed state.
In the paper-reversing device of this type, the tray 202 tilts with its paper-sending side facing up; therefore, the oncoming paper is allowed to slide over the preceding paper located on the tray 202 and reach the paper-stopping member 203. This makes it possible to provide continuous paper-reversing operations.
The paper-transporting capability in a paper-reversing device, that is, the copying capability concerning how many copies can be made per one minute in a copying machine having the paper-reversing device, is determined by a paper-transporting speed and paper intervals (the distance between any two sheets of paper) during a paper-transporting process. Therefore, when it is impossible to increase the paper-transporting speed in order to improve the copying capability, it is necessary to narrow the paper intervals during the paper-transporting process.
However, in the above-mentioned paper-reversing device, no paper can be fed onto the tray 202 during the time when the paper, located at the lowest position on the tray 202, is sent by shifting the paper-stopping member 203 and rotating the transport belt 204. For this reason, it is difficult to shorten the paper intervals, and consequently difficult to obtain sufficient paper-transporting capability, that is, sufficient copying capability.
Moreover, in the above-mentioned paper-reversing device, when the size of paper is changed, it is necessary to adjust the positioning of the paper-stopping member 203 in response to the change. This requires a complicated mechanism, thereby resulting in a complicated construction. Furthermore, in the above-mentioned paper-reversing device, when paper is sent onto the tray 202, it is necessary to suck the paper onto the transport belt 204 by the use of air suction. For this reason, the transportation of paper cannot be started until the paper has been positively sucked onto the transport belt 204, and this also makes it impossible to shorten the paper intervals.